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.Dd December 29, 2019
.Dt GNOP 8
.Os
.Sh NAME
.Nm gnop
.Nd "control utility for NOP GEOM class"
.Sh SYNOPSIS
.Nm
.Cm create
.Op Fl v
.Op Fl c Ar count_until_fail
.Op Fl d Ar delaymsec
.Op Fl e Ar error
.Op Fl o Ar offset
.Op Fl p Ar stripesize
.Op Fl P Ar stripeoffset
.Op Fl q Ar rdelayprob
.Op Fl r Ar rfailprob
.Op Fl s Ar size
.Op Fl S Ar secsize
.Op Fl w Ar wfailprob
.Op Fl x Ar wdelayprob
.Op Fl z Ar physpath
.Op Fl Z Ar gnopname
.Ar dev ...
.Nm
.Cm configure
.Op Fl v
.Op Fl c Ar count_until_fail
.Op Fl d Ar delaymsec
.Op Fl e Ar error
.Op Fl q Ar rdelayprob
.Op Fl r Ar rfailprob
.Op Fl w Ar wfailprob
.Op Fl x Ar wdelayprob
.Ar prov ...
.Nm
.Cm destroy
.Op Fl fv
.Ar prov ...
.Nm
.Cm reset
.Op Fl v
.Ar prov ...
.Nm
.Cm list
.Nm
.Cm status
.Nm
.Cm load
.Nm
.Cm unload
.Sh DESCRIPTION
The
.Nm
utility is used for setting up transparent providers on existing ones.
Its main purpose is testing other GEOM classes, as it allows forced provider
removal and I/O error simulation with a given probability.
It also gathers statistics on the number of read, write, delete,
getattr, flush, and other requests, and the number of bytes read and written.
.Nm
can also be used as a good starting point for implementing new GEOM
classes.
.Pp
The first argument to
.Nm
indicates an action to be performed:
.Bl -tag -width ".Cm configure"
.It Cm create
Set up a transparent provider on the given devices.
If the operation succeeds, the new provider should appear with name
.Pa /dev/ Ns Ao Ar dev Ac Ns Pa .nop .
The kernel module
.Pa geom_nop.ko
will be loaded if it is not loaded already.
.It Cm configure
Configure existing transparent provider.
At the moment it is only used for changing failure probability.
.It Cm destroy
Turn off the given transparent providers.
.It Cm reset
Reset statistics for the given transparent providers.
.It Cm list
See
.Xr geom 8 .
.It Cm status
See
.Xr geom 8 .
.It Cm load
See
.Xr geom 8 .
.It Cm unload
See
.Xr geom 8 .
.El
.Pp
Additional options:
.Bl -tag -width "-c count_until_fail"
.It Fl c Ar count_until_fail
Specifies the number of I/O requests to allow before setting the read, write and
delay failure probabilities.
.It Fl d Ar delaymsec
Specifies the delay of the requests in milliseconds.
Note that requests will be delayed before they are sent to the backing device.
.It Fl e Ar error
Specifies the error number to return on failure.
.It Fl f
Force the removal of the specified provider.
.It Fl o Ar offset
Where to begin on the original provider.
.It Fl p Ar stripesize
Value of the stripesize property of the transparent provider.
.It Fl P Ar stripeoffset
Value of the stripeoffset property of the transparent provider.
.It Fl q Ar rdelayprob
Specifies read delay probability in percent.
.It Fl r Ar rfailprob
Specifies read failure probability in percent.
.It Fl s Ar size
Size of the transparent provider.
.It Fl S Ar secsize
Sector size of the transparent provider.
.It Fl w Ar wfailprob
Specifies write failure probability in percent.
.It Fl v
Be more verbose.
.It Fl x Ar wdelayprob
Specifies write delay probability in percent.
.It Fl z Ar physpath
Physical path of the transparent provider.
.It Fl Z Ar gnopname
The name of the new provider.
The suffix
.Dq .nop
will be appended to the provider name.
.El
.Sh SYSCTL VARIABLES
The following
.Xr sysctl 8
variables can be used to control the behavior of the
.Nm NOP
GEOM class.
The default value is shown next to each variable.
.Bl -tag -width indent
.It Va kern.geom.nop.debug : No 0
Debug level of the
.Nm NOP
GEOM class.
This can be set to a number between 0 and 2 inclusive.
If set to 0, minimal debug information is printed.
If set to 1, basic debug information is logged along with the I/O requests
that were returned as errors.
If set to 2, the maximum amount of debug information is printed including
all I/O requests.
.El
.Sh EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
.Sh EXAMPLES
The following example shows how to create a transparent provider for disk
.Pa /dev/da0
with 50% write failure probability, and how to destroy it.
.Bd -literal -offset indent
gnop create -v -w 50 da0
gnop destroy -v da0.nop
.Ed
.Pp
The traffic statistics for the given transparent providers can be obtained
with the
.Cm list
command.
The example below shows the number of bytes written with
.Xr newfs 8 :
.Bd -literal -offset indent
gnop create da0
newfs /dev/da0.nop
gnop list
.Ed
.Sh SEE ALSO
.Xr geom 4 ,
.Xr geom 8
.Sh HISTORY
The
.Nm
utility appeared in
.Fx 5.3 .
.Sh AUTHORS
.An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org
